The present invention relates generally to articulated beds having a foundation and a mattress thereon and which are adjustable to provide the desired contoured support to the user lying on the mattress. It more particularly relates to such beds which are driven by one (or more) electrical motor(s) and whose head portion can be pivoted by that motor between a flat orientation and a raised orientation.
Adjustable beds have been used for many years to alter the contours of top surfaces of mattresses to thereby adjust the support on the different portions of the bodies of persons lying on the mattresses. This support adjustment can be for therapeutic purposes, for comfort reasons, or for the user's convenience, as when the user who was previously sleeping now wants to sit propped up to read, eat or watch television. Originally, this adjustment was by manually-operated mechanical levers or cranks. Later, these manually-operated mechanical devices were replaced by one or more motors which drove the adjustable bed into the desired position through gear trains, chain drives, sprocket drives, or threaded shafts.
Adjustable beds are typically used in hospitals or convalescent homes by patients who must spend long periods of time in bed for health, injury or physical handicap reasons. The use of adjustable beds in private homes has increased markedly though in recent years. This is due to the popularity of home television and video viewing, the aging of the population and the technical advances which have been made in the construction, operation and capabilities of adjustable beds.
Examples of adjustable beds known in the prior art are shown in U.S. Pat. Nos. 4,381,571, 4,385,410 and 4,407,030. All of these patents are owned by the present assignee and are hereby incorporated by reference. Additionally, an adjustable bed representative of the prior art is illustrated generally at 50 in FIG. 1 and discussed below.
The conventional adjustable bed 50 has a motor-driven, articulated bed platform plate for supporting and moving equal-length top and foundation mattresses 54, 56. The foundation mattress 56 is usually a cloth-covered foam layer glued to the articulated platform plate, or it can be a box spring similarly attached. When the bed 50 is flat, which is its normal position, the top and foundation mattresses 54, 56 are the same length. When the bed platform shown generally at 57 is operated to cause the mattresses 54, 56 to assume curved shapes, as shown in FIG. 1, the length of the mostly concave top surface of the foundation mattress is noticeably shortened relative to the mostly convex bottom surface of the top mattress. The user's buttocks often are pinched in the crease of the mattress, as shown by reference numeral 58. Also, as the head sections of the mattresses are pivotally raised, an undue amount of compression is placed on the lower mattress 56 at the crease or bend.
The conventional adjustable bed 50 has a footboard or mattress guard 60 to restrain the foot of the top mattress 54 from projecting beyond the foot of the foundation mattress 56. When the bed 50 is curved, the top mattress 54 rides up over the foundation mattress 56 so the head of the top mattress extends beyond the head of the foundation mattress. The top mattress 54 thereby overhangs the bottom foundation 56, as shown generally by reference numeral 62, adversely effecting the wear and comfort features of the head portion of the mattress 54. Also, the frictional sliding of the top mattress 54 over the foundation mattress 56 dissipates energy, increasing the work that must be performed by the motor which adjusts the bed platform plate. In addition when raising the head end of the mattress 54 towards the foot of the bed 50, stationary nearby objects which were originally near the head of the user 64, for example a lamp 66, a radio or a telephone 68 on adjacent night tables or night stands 70, 72, are now behind the user and out of his or her convenient reach.